For many years, down, and down mixed with feathers, were the predominant products for use as filling materials for pillows and sleeping bags. Although durability and resilience are very good (so long as they are not wetted), down and down/feather blends have significant deficiencies. They matt when washed, so dry cleaning is recommended in contrast to home-laundering. The feather quills poke through the ticking and the down passes through the ticking, resulting in loss of pillow height. Many people are allergic to feathers and down. Furthermore, down is very expensive. To overcome these limitations, crimped synthetic staple fiber, particularly polyester fiberfill, has been used as a filling material for pillows instead of down. Synthetic "staple fiber" has been cut so as to provide short discontinuous pieces of a desired length or "staple".
Initial attempts to use polyester fiberfill cut staple fiber as filling material were disappointing because staple fiber filling material tended to clump after prolonged use. A steady stream of modifications leading to improved performance of filling materials have appeared over the years. One of the first developments was the use of slickeners to permit the fibers to slip past each other more readily, which reduced the tendency to clump, as disclosed, for example, in U.S. Pat. No. 3,271,189. The use of hollow fibers as polyester fiber fill staple in place of solid fibers was described by Tolliver in U.S. Pat. No. 3,772,137. An important recent development was the introduction of very small fiberballs, sometimes referred to as "puffs" or as rounded clusters of staple fibers, as filling material. The preparation and properties of fiberballs are described by Marcus in U.S. Pat. Nos. 4,618,531 and 4,794,038. Snyder, et al, U.S. Pat. No. 5,218,740 and Halm, et al, U.S. Pat. No. 5,112,684, for example, describe different techniques for preparing fiberballs or rounded fiber clusters.
From a review of the patent literature it is apparent that efforts to improve the performance of pillows have been focused on the filling material. The nature or identity of the ticking material is rarely mentioned, although it is believed that the pillow trade has recognized that the appearance and tactile qualities of the ticking can be important elements of customer appeal.
For clarification, a pillow is normally sold as illustrated in FIGS. 1 and 2 of the accompanying drawings, wherein FIG. 1 is a perspective view, and FIG. 2 is a view in section in direction 2--2 shown in FIG. 1. The pillow, shown generally as 11, comprises an outer fabric covering 12, which is referred to in the trade as a "ticking", that surrounds the filling material, shown schematically as 13, which may be loose staple fiber, but was generally in the form of a rolled batt, as disclosed, e.g., by LeVan in U.S. Pat. No. 3,510,888, or more recently as very small fiberballs or clusters, as mentioned above, or can be in the form of deregistered continuous filamentary tow, as disclosed, e.g., by Watson in U.S. Pat. Nos. 3,328,850 and 3,952,134. The ticking generally has a zipper (not shown) or other means whereby it may be opened and closed for introducing, removing and retaining the filling material.
In use, such pillows are generally provided with a removable pillow slip, for convenience for laundering separately, without the need for washing the pillow, and for aesthetics, e.g., to match other bed linen which may be varied from time to time. Such a pillow slip is not to be confused with the ticking that is referred to herein. Traditionally, pillow ticking fabrics have often been striped and made of yarns spun (i.e., formed by twisting together) from durable hard-wearing cotton (which is a natural staple fiber) or other staple fiber. When the term "spun yarn" has been used, this term has been used to indicate yarns that have been formed by spinning cotton and/or synthetic cut fibers into a continuous strand; in other words, discontinuous fibers have been spun (as, for example, on an old-fashioned spinning wheel), i.e., twisted together into a continuous strand (or yarn) of such discontinuous fibers. The term "spun yarn" has not been used in the trade to refer to yarns of continuous filaments, such as silk or continuous synthetic filaments. So far as is known, wholly continuous filament synthetic polymer fabrics have not been used to make pillow tickings, although they have been used to enclose fiberfill in other filled articles, such as apparel, sleeping bags and comforters.
It has now been found, according to the invention, that ticking fabrics wholly of synthetic polyester continuous filaments, especially containing subdenier filaments, can have an unexpected influence on the physical behavior of pillows.